Tool holding fixture

ABSTRACT

A tool holding fixture having a rotationally symmetrical holding body and a shaft that form one piece. The one piece has an axially directed first annular groove which is concentric with the shaft and is positioned in a transition area between the holding body and the shaft. The shaft has an annular collar with a flank which is inclined in a direction toward the first groove. The rotatable clamping ring encompasses the collar and engages the first annular groove. The rotatable clamping ring is seated on the shaft. The clamping ring has a second annular groove in which wedge-shaped sliding blocks are seated and are radially and axially moveable, but secured against canting within the second groove. The sliding blocks are supported on the inclined flank of the collar. A pressure screw is threadedly engaged within the clamping ring.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a device for setting the true running of atool holder. Great importance is assigned to the true running ofrotating tools. Precise true running results in a longer service life ofthe tools, particularly tools associated with milling, drilling andreaming, and accordingly results in fewer interruptions for changing thetools. Also, the tools need not be re-sharpened as often, so that theuse of the tools is improved and costs are lowered. Deviations from truerunning lead to radially disruptive forces which not only damage thetools and cause increased wear, but also cause reduced dimensionalaccuracy of the work pieces to be processed. Accordingly, it isdesirable to be able to set true running as accurately as possible.

2. Description of Prior Art

Up to now it has been attempted to produce holder bodies with highlyaccurate true running. Miscellaneous defects which are a function of thetool or which are created when clamping the tool have not beencompensated.

Recently, holder bodies have been disclosed having a correction providedfor compensating the deviation generated during clamping of the tool.This is accomplished with specially produced eccentric grinding of theconical holder body.

Also known are multi-part basic holders for setting true runningfollowing clamping of the tool. In addition to the relativelycomplicated adjustment of such multi-part basic holder bodies, stabilityis also effected in such structures.

SUMMARY OF THE INVENTION

It is therefore one object of this invention to provide a device inwhich true running of a one-piece tool holder can be set. In particular,it is intended that this setting take place at the machine itself, withthe holder body installed and the tool in a clamped position.

This object is achieved with a device for setting the true running of atool holder having a rotationally symmetrical holding body and a shaftforming one piece with an axially directed first annular groove that isconcentric with the shaft and in a transition area between the holdingbody and the shaft. The shaft has an annular collar with a flankinclined in a direction toward the first groove. A rotatable clampingring encompasses the collar and engages the first annular groove, and isseated on the shaft. The clamping ring has a second annular groove inwhich wedge-shaped sliding blocks are seated and are radially andaxially moveable, but secured against canting within the second groove.The sliding blocks are supported on the inclined flank of the collar,and a pressure screw is threadedly engaged within the clamping ring.

If such setting is performed directly on the machine, all accumulatedtrue running errors which result from the tool via the clamping cheeksand the receiver, including the steep angle tapered holder as far as thespindle bearing deviations, can be compensated. Particularlyadvantageous embodiments of this invention are set forth in thedependent claims and in the following specification.

BRIEF DESCRIPTION OF THE DRAWINGS

One preferred embodiment of this invention is shown in the drawings andexplained in the following specification, wherein:

FIG. 1 is an axial, longitudinal sectional view of a tool holdingfixture with a true running set device, according to one preferredembodiment of this invention;

FIG. 2 is a cross section taken along line A--A of FIG. 1; and

FIG. 3 is a side view of the clamping ring.

DESCRIPTION OF PREFERRED EMBODIMENTS

The tool holding fixture, essentially conventional in shape, comprises arotationally symmetrical holding body 1 and a shaft 2 connectedtherewith. The holding body 1 and the shaft 2 form a one-piece unit,preferably machined from round bar steel. The holding body 1 isrotationally symmetrical and generally shown in the drawing as a steepangle tapered cone. It is apparent that any other rotationallysymmetrical holder can be used in lieu of the steep angle taperedholder. For this reason, only a rotationally symmetrical holding body 1will be mentioned below. The holding body 1 has an increased diameter inthe area of its transition to the shaft 2. An axially directed annulargroove 3 is cut into the shoulder. The groove 3 extending concentricallyaround the shaft 2 is shaped in such a way that its inner wall is formedby the shaft 2. The shaft 2 has an annular collar 4 spaced from thebottom of the groove 3 by approximately the radius of the shaft 2. Thecollar 4 is also formed in one piece with the shaft 2. The annularcollar 4 has a flank 5 inclined in the direction of the groove 3. Theinclination of the groove 3 is approximately 45° with respect to thelongitudinal axis of the shaft 2.

The opposite flank of the collar 4 extends at least approximatelyradially outward from the shaft 2. The height of the collar 4 is lessthan the width of the circumferential annular groove 3.

A rotatable clamping ring 10 is mounted on the shaft 2. The through-bore19 on the front of the clamping ring 10 is adapted in an exactly fittingmanner to the shaft 2 of the tool holding fixture. The jacket wall ofthe clamping ring 10 is tapered at its back end to such a degree thatthe clamping ring 10 fits with a tolerance into the annular groove 3 ofthe holding body 1. A circumferential groove 10' with a square crosssection is cut into the inside of the clamping ring 10, in which twosliding blocks 11 and 12 are seated and are located diametricallyopposite each other. Although the sliding blocks 11 and 12 are seatedmovably in the radial and axial direction in respect to the shaft 2,they are secured against twisting in the groove 3. Both sliding blocks11 and 12 have inclined edges 17 which are adapted to the inclination ofthe flank 5 of the collar 4. An axially, inwardly directed pressurescrew 13 presses on the sliding block 12, on the bottom as shown in thedrawing. The screw 13 is embodied, for example, as a stud screw with ahexagon socket. It is possible to apply pressure on the sliding block 12with the screw 13 and thus a tensile force is exerted on the shaft 2 andpressure is conducted to the holding body I via the clamping ring 10.The clamping ring 10 has an appropriate raised surface 15 on its frontface 14, so that the pressure force is transferred from the clampingring 10 to the holding body 1 outside of the center and asymmetrically.

As a result a bending torque is exerted on the shaft 2 in the directionof the arrow B. Thus, the clamping ring 10 naturally performs a slightcanting or tilting movement. The clamping ring 10 must be received withplay or a tolerance in the groove 3 to assure tilting movement, aspreviously described. The tilting movement, which actually is more of aslight deformation of the clamping ring 10 and a slight bending of theshaft 2, also requires a small amount of freedom of movement of thesliding block 12 on which the pressure screw 13 acts. So that thesliding block 12 does not tilt in the groove 10' so that the clampingring 10 is therefore jammed on the shaft 2, the sliding block 12 ispartially slanted on its front face 18 which is oriented towards thegroove 3.

The transmission ratio, which by means of many geometric factors of theconstruction, such as the diameter, is a function of the inclination ofthe slanted flank 5 of the collar 4 and of the inclined edge 17 on thesliding blocks 11 and 12.

With this invention, it is possible to perform the setting of truerunning either on the tool holding fixture alone or, as alreadypreviously described, with the tool clamped. This can take place eitherwith a conventional pre-setting apparatus or with a stand and indicatingcaliper directly on the machine. For this purpose first the highestpoint is determined, after which the clamping ring 10 is turned so thata marking cut 16 applied to its exterior is aligned with this highestpoint. Now the pressure screw 13 is tightened to such an extent that thehighest point is set back by half of the deflection of the indicatingcaliper. With this the setting is complete. Thus, the true running errorcan be reduced to an order of magnitude of 0.001 mm. Although, ofcourse, different geometrical arrangements of the various structuralelements by means of which the desired bending torque can be exerted onthe shaft are possible. An economically preferred solution is the oneshown in the drawings, having only two diagonally, oppositely locatedsliding blocks 11 and 12. For example, the desired bending element couldalso be formed by a part inserted in the annular groove 3, but this is amore complex solution. It is particularly advantageous to dispose theraised surface 15 on the clamping ring 10 on a side diametricallyopposite the pressure screw 13. Thus, the lever is maximally embodied.

It may be advantageous to provide the annular groove 3 with an outwardlyinclined lateral wall and to provide the rise, which is then supportedby this lateral wall, with an equally inclined stop face. This mayperhaps reduce the specific pressure and reduce the danger of a notchingeffect.

I claim:
 1. A device for setting the true running of a tool holdingfixture, comprising: a rotationally symmetrical holding body (1) and ashaft (2) forming one piece, said one piece having an axially directedfirst annular groove (3) concentric with the shaft (2) in a transitionarea between said holding body (1) and said shaft (2), said shaft (2)having an annular collar (4) with a flank (5) inclined in a directiontoward said first groove (3), a rotatable clamping ring (10)encompassing said collar (4) and engaging said first annular groove (3)being seated on said shaft (2), said clamping ring (10) having a secondannular groove (10') in which a plurality of wedge-shaped sliding blocks(11, 12) are seated and are radially and axially movable but securedagainst canting within said second groove (10'), said sliding blocks(11, 12) supported on said inclined flank (5) of said collar (4), and apressure screw (13) threadedly engaged within said clamping ring (10).2. A device in accordance with claim 1, wherein said clamping ring (10)has a raised surface (15) on a front face (14) of said clamping ring(10) which is positioned within said first annular groove (3).
 3. Adevice in accordance with claim 2, wherein said raised surface (15) ofsaid clamping ring (10) is positioned on a side located diametricallyopposite said pressure screw (13).
 4. A device in accordance with claim2, wherein said clamping ring (10) has a marking cut (16) positioned onan outer periphery of said clamping ring (10) and said marking cut (16)is oriented towards a center of said raised surface (15).
 5. A device inaccordance with claim 1, wherein said sliding blocks (11, 12) haveinclined edges (17) which have at least approximately a same degree ofslant as said inclined flank (5) of said collar (4).
 6. A device inaccordance with claim 1, wherein one said sliding block (12) ispositioned near said pressure screw (13) and has a front face (18)inclined towards said first annular groove (3).
 7. A device inaccordance with claim 1, wherein said holding body (1) has a taperedholder (6).
 8. A device in accordance with claim 2, wherein said firstannular groove (3) has an outwardly inclined wall having a rise thatrests with a stop face of said clamping ring (10) which is approximatelyequally slanted.